As Britain awaits the birth of a royal baby, supposedly third in line for the throne, I wonder if there is a minimum age when it comes to secession? Let’s say something bad happens to the Queen and the other two heirs. At what age does the Royal Rug Rat become the King/Queen, and who rules the country until then?
18
A regent. Probably one of his uncles.
As I understand it, he’d be the king immediately, but the appointed Regent would do all the kinging until he turns 18.
Succession. 
Whoops.
Oh, and it’s a boy.
As has been said, the age of succession is 18. This is governed by the Regency Acts passed in 1937, 1943 and 1953, which also govern what would happen if the reigning monarch becomes unable to rule (say, through mental incapacitation). Also when the monarch is abroad or only temporarily ill a Council of State will carry out the functions of the monarchy.
the heir become king immediately, on the principle of “the king is dead, long live the king”. A Regent would exercise the functions of the Crown until 18.
If something were to happen, I wouldn’t be surprised to see a Regency in effect until His Nibs had completed university and possibly a tour in the Services.
Yes, but we’ve had a regent for an adult monarch before: King George III. Are you really going to expect the Monarch to fit in a part-time degree at the Open University while performing all his official duties? Of course not. In the posited scenario, I can see a Regent being in place until the King has attended university and a tour in the Armed Services
That might qualify under the “some definite cause” part:
When Victoria was the eleven year old heir, the British government designated her mother, the Duchess of Kent, as the regent if her uncle, King William IV, died. William greatly disliked his sister-in-law and swore he would stay alive until Victoria turned eighteen. He did it and died three weeks after her eighteenth birthday.
The reason for Victoria’s mother being suggested as Regent was probably because the next in line to the throne, Prince Ernest, Duke of Cumberland, was widely mistrusted. He was alleged to have murdered his valet and fathered a child on one of his own sisters, and it was rumoured that he had ambitions to displace Victoria.
As it happened, when Victoria succeeded, he went off to become King of Hanover.
So if something were to happen to the queen, Charles, and William, the new baby would be come king and the Regency would fall to… Harry? He would be the next qualified heir no?
Prince Andrew would be my guess.
What I find a little interesting about this, is that 18 is actually younger than the medieval age of majority in England. Henry III was a little past 19 when he assumed full regal power and most did not consider him at full majority until he was 21 ( there were legal disputes about the grants he made between those ages ). Richard II didn’t achieve his majority until age 22. Roman law argued for 25.
No, Harry would be the next in line, as suggested, and Regent according to the currently enacted Regency Acts. Note that those were passed in this century, and did not apply to earlier regencies. As Charles has more grandchildren, which is likely, Andrew gets pushed further and further down the list.
Actually, 18 is older then when several monarchs took power in their own right (without a regent).
Henry VI became king at the age of nine months and was declared of age at 11.
Edward V was king at age 12 and was considered old enough at that point to reign. Richard III postponed his coronation and locked him up in the tower of London to keep power.
Technically, Richard II reigned from age 11; there was no regent, though his advisers held the real power.
Before some wiseacre points it out, by “in this century”, I meant “in the last 100 years”. Darned short edit window.